The present invention relates, in general, to a heat transfer device for electronic components, and more particularly is directed to a heat transfer device having a cylindrical stator portion carrying a plurality of spaced annular cooling fins and a rotor which carries wiper fins extending into annular slots between the cooling fins for moving heated air out of the stator.
As electronic components are made smaller and smaller, the problem of heat dissipation tends to increase, not only because the components may generate more heat as a result of the size decrease, but because they may generate more heat per unit area on a circuit board, for example. This heat problem becomes acute in the computer industry, where typically there are a large number of circuit components in a restricted area, such as on a printed circuit board. Many of these components, particularly high power devices, generate a great deal of heat, and a need exists for a device to cool such devices effectively and efficiently.
Most heat transfer devices presently available and in use today are static heat sinks which are secured to a heat source and which contain no moving parts. Such devices typically consist of a body portion contacting the heat source and a large number of fins extending from the body portion through which air flows to remove heat. Typically, the devices rely on air convection to remove the heat, or rely on a fan which forces air across the fins. In the first case, the heat transfer is inefficient and often slow, while in the second case the use of fans or blowers increases power consumption and may require special power supplies. Furthermore, fan or blower devices can be noisy, may induce vibration, and generally have a relatively limited life, and often require the use of a blower speed control to limit the shifting of thermal gradients. Another difficulty encountered in prior heat sink devices is that boundary layers form in the cooling fluid in the boundary areas between the heat sink cooling fins and the moving fluid. Thermal boundary layers reduce the thermal gradient adjacent to the cooling fins and thus interfere with the efficient cooling of the fins. Momentum boundary layers reduce the velocity, and thus the flow, of the cooling fluid adjacent to the cooling fins. This also reduces the effectiveness of the heat sink. Prior heat sink devices have traditionally been designed so that the momentum boundary layer at one fin will not develop to a thickness that will cause it to meet the boundary layer developing at the next adjacent fin. However, such structures, unlike the dynamic heat sink, do not prevent the development of momentum and thermal boundary layers.